I agree with the M105/205 combo.
I suggest the 105 with the Meguiar's 7006 cutting pad. You can use a more aggressive pad with this polish, but I think this combo is safe for most beginners who want to get rid of moderate imperfections.
http://www.autogeek.net/mgw7006.html
... and the 205 with the 8006 polishing pad
http://www.autogeek.net/mgw8006.html
again- you can use a stronger pad (such as Lake County's), but IMO this is good for someone just getting into it.
The 105 polish is pretty aggressive and finishes down really quick. The 105 takes a little more work but you'll be very impressed with the results.